1 Field of the Invention
This invention relates to omnidirectional ultrasonic intrusion surveillance unit.
2. Description of the Prior Art
Such surveillance units at the present time are bulky, requiring three monthly maintenance, expensive and are of a sensitive nature giving rise to "False Alarms". They operate either by use of single transducer heads in separate instruments reacting upon each other, or with two heads within one instrument. The field covered by such an instrument is limited to the area forward of the transducer head usually in the order of 160.degree. in two planes. Such an instrument can easily be attacked and neutralized by a determined intruder.